This invention relates generally to wrenches and, more particularly, is directed to an open ended ratchet spanner.
In many tight fitting situations, it is difficult to use a conventional ratchet wrench. Therefore, a conventional open ended wrench must be used. However, in tightening a bolt, for example, the wrench must continuously be removed from the bolt head (or nut) and then replaced thereon at a different angle for tightening or loosening the same. This procedure is continued until the bolt is tightened or loosened. In other words, the spanner arm can only be turned a few degrees at a time.
In this regard, open ended ratchet spanners have been developed having a configuration similar to open ended wrenches, and which can thereby fit within such tight spaces. For example, U.S. Pat. Nos. 1,169,007; 2,376,575 and 2,760,394 disclose such a ratchet spanner having an arcuate jaw-like head connected with a handle. The jaw-like head includes a substantially continuous, arcuate, inner side wall having a plurality of pockets, each receiving a pawl. A ratchet insert member having a plurality of teeth is positioned in the space defined by the inner side wall, with the pawls being engageable with the teeth to provide a ratchet operation, with each of the pawls being spring biased into engagement with the teeth. Specifically, a separate coil spring is separately associated with each pawl for normally biasing that pawl in a direction into engagement with the teeth of the ratchet member. As will be appreciated, particularly from U.S. Pat. No. 2,760,394, where there are a plurality of pawls, it becomes cumbersome, time consuming and expensive to individually set the coil springs with respect to the pawls. In addition, with such known ratchet spanners having an open jaw configuration, and within certain ranges of friction when turning the bolt or nut, the pawls tend to lock with the teeth, and because of the high spring pressure of the coil springs, do not release again. As a result, there is no ratchet action, and the bolt or nut turns with the spanner. Therefore, the ratchet spanner must be removed from the bolt or nut in order to remedy the same. Such high spring pressure presents still another disadvantage. Specifically, the ratchet spanner cannot be removed radially from the nut or bolt until the ratchet insert member is rotated to a predetermined angle with respect to the jaw-like head, so as to provide an open end to the spanner. However, due to the high spring pressure, this cannot be performed without the use of an additional tool.
However, biasing the pawls only by coil springs as in the DE-PS 3,129,710 corresponds practically to positioning in a free floating manner and may result in inaccuracies in alignment, and difficulties in removing the pawls from engagement with the teeth.
Further in these known ratchet spanners with an open jaw the locking of the pawls into the tooth gaps must be performed under relative high contact pressure of the flexible structural parts which may lead to the following problems.
1. When reaching a given frictional end position the pawls lock, but because of the strong spring pressure they do not release again, so that during the actuating of the ratchet spanner arm the nut and the structural part to be screwed on follow the reciprocal movement of the ratchet spanner arm, and no turning around of the structural part can be achieved; PA0 2. During at least some operations the nut will assume an end position which enables a radial removal of the tool only in case the nut, after being axially removed from the work piece, is manually pivoted to such an extent that its jaw is flush with the spanner head. However this cannot be performed without the use of an additional tool due to the high spring pressure which blocks the nut.
Finally in German Patent 835,877 a ratchet spanner is disclosed in which the pawls are substituted by leaf springs being themselves the arresting or ratchet means which is clearly unsuitable in case that high torque stresses are applied.